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Canon "DO"
Russell Price:
Estoooo...¿de qué van esos objetivos "DO" de Canon? Estoy un poco desconectado y no sé de qué va.Y como Jrodri se va a comprar uno,según leo en uno de sus posts,pues me he acordado de preguntar.
Graciassssss! :)
Goala:
DO = diffractive optics
Copio y pego de esta página....
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How do diffractive optics work?
Diffraction is normally viewed as a problem in photographic lenses, causing light scatter at small apertures. Canon is the first, and so far the only, lens manufacturer to use diffractive optics to focus light. The diffractive element contains embedded optical plastic parts with a series of moulded concentric rings which bend light more steeply than conventional refractive lenses. The first DO lens produced, the 400 DO, had two of these but for a zoom lens, where the angle of light passing through varies with focal length, a third was needed with an air space. A major advantage of a DO lens group is that chromatic aberration is reversed compared with normal refractive elements so by combining both types, chromatic aberration, the major cause of loss of sharpness at long focal lengths, can be almost cancelled out.
What was the optical performance like in real life photographic situations? In bright light, with the sun above or to the rear, sharpness and colour saturation were good, even at full aperture. On a variety of subjects the fine detail revealed after light USM (200%, 0.3 pixels) was impressive. However I soon started to notice a dreamy quality to some of the photos, especially around white subjects, when photographing into the light. Even using the lens hood I got substantial multi-coloured flare when photographing into low light when the light source was just out of the frame. Highlights from water revealed obvious target-shaped discs. When I used a mirror lens many years ago I got to like the doughnut shaped out-of-focus effects and often framed pictures to maximise the effect. I found myself doing the same thing with this lens when photographing a sea bird colony. Out of focus areas also had a ‘broken’ quality with leaves sub-divided and fine details like grasses repeated.
So the lens is capable of high quality results in most lighting conditions but in back-lit situations, which I do a lot of, light scatter within the lens, almost certainly from the diffractive group, can lead to variable loss of quality. Heavier than normal Unsharp Masking can improve some of this as it increases the contrast at edges, where this dreamy quality is most obvious, but this should not be necessary in a £1,000 lens.
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Y aquí información oficial de Canon.
Saludos ;)
Russell Price:
Gracias,Goala.
O sea,que los objetivos de Canon terminarán siendo "de todo a un euro" o L-USM-IS-DO y costarán un ojo de la cara (más).
Bien.
Sergio Blanco:
--- Cita de: Russell Price ---Estoooo...¿de qué van esos objetivos "DO" de Canon? Estoy un poco desconectado y no sé de qué va.Y como Jrodri se va a comprar uno,según leo en uno de sus posts,pues me he acordado de preguntar.
Graciassssss! :)
--- Fin de la cita ---
Hola Russell, tienes una prueba publicada en Caborian sobre uno de estos objetivos.
http://www.caborian.com/index.php?option=com_content&task=view&id=305&Itemid=64
Saludos.
Russell Price:
Gracias,Sergio! :)
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